This application relates generally to a mixer for a gas turbine engine wherein the mixer includes a scoop that is thermally decoupled from the mixer.
Conventional gas turbine engines include an intake section, a compressor, a combustor, a turbine assembly, and a tail section. The intake section includes a fan, which delivers intake air to both the compressor and a mixer located at the tail section.
Intake air enters the engine through the intake section. The intake air delivered to the compressor is compressed and delivered primarily to the combustor where the compressed air and fuel are mixed and burned in a constant pressure process. The by-products of the combustion process exit the engine through the tail section at an elevated temperature as exhaust.
The intake air, which is delivered to the mixer by the fan through a series of scoops attached to the mixer, is at a lower temperature than the exhaust. The lower temperature intake air mixes with the exhaust to reduce the temperature of the exhaust.
Traditionally, each scoop is fixedly attached to the mixer via an elaborate series of brackets, which are riveted to both the mixer and the scoop. As such, the traditional bracket/rivet attachment configuration is extensive, adding weight and, in turn, cost to the final engine assembly.
In addition, the traditional bracket/rivet attachment configuration is very rigid. Because the mixer receives exhaust at an elevated temperature and the scoops receive intake air at a much lower temperature, the mixer itself has the tendency to expand and contract to a greater degree than the scoops. As such, a thermal fight exists between the mixer and the scoop resulting in low cycle fatigue and high cycle fatigue cracking.